The effects of genotype, sex and feeding regimen on pig carcass development: 2. Tissue weight distribution and fat partition between depots

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Abstract
SUMMARY: Dissection data for 1006 carcasses taken from the first 2 years of the Meat and Livestock Commission's (MLC) Commercial Pig Evaluation (CPE) were used to examine the growth of tissue weights in joints relative to the corresponding total tissue weight in carcass, and the growth of fat depots relative to total fat over the carcass weight range, 46–92 kg. Growth relationships were examined using a linear allometric model. Differences in tissue weight distribution between genotypes (pigs from different companies in CPE), sexes (barrows and gilts) and feeding regimens (restricted and ad libitum feeding) were examined at constant lean, bone or fat weight as appropriate, common allometric regression slopes being assumed.Lean and bone showed the same pattern of development. Relative growth was lowest in the proximal limb joints (ham and hand) increasing inwards to the joints of the back. With minor differences, the same pattern was found for subcutaneous fat and intermuscular fat. Fat depots differed considerably in their growth relative to total fat: intermuscular fat grew more slowly (allometric growth coefficient, b = 0·87), subcutaneous fat at the same rate and perinephric and retroperitoneal fat (flare fat) more rapidly (b = 1·24).Significant differences were recorded between genotypes in lean distribution and in the distribution of fat depots. However, the differences were small and of little commercial importance. There were also differences in fat partition between genotypes, flare fat being the most variable depot.Sex and feeding regimen also influenced tissue distribution and fat partition.The results are discussed in relation to the robustness of regression equations for predicting overall carcass composition from subcutaneous fat measurements and sample joint dissections.